No Ack in IEEE 802.11e Single-Hop Ad-Hoc VoIP Networks

This paper analyzes the impact of the No Ack policy in VoIP ad-hoc single-hop IEEE 802.11e networks. The No Ack policy consists on suppressing the MAC layer acknowledgement packets. This option dramatically reduces the duration of MAC frames and thus increments the maximum number of VoIP flows that can coexist in the network. The negative side is an increased packet loss rate and the consequent drop of voice quality as perceived by the users. The article presents a model to quantify the benefits of suppressing acks and assess the viability of the No Ack policy. It follows an argumentation to identify which is the best codec to combine with acknowledgement suppression and in which conditions the usage of No Ack can be beneficial. Finally, it is suggested to modify the stations to switch to No Ack policy as the network approaches congestion.